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Full text of "New equipment for obtaining host material for the mass production of Trichogramma minutum, an egg parasite of various insect pests"

.•».VJ. 




Historic, archived document 

Do not assume content reflects current 
scientific knowledge, policies, or practices. 



y y ' f ' 



0. S, DEPT. OF AGRieULTOSt^ 

RATIONAL AGRICULTURAL LIBRAftf 

DEC 28 1976 

IKOeUREMENT SECTION 
fiUKXENTSIRIAl RECORDS 




CIRCULAR No. 376 DECEMBER 1935 \\ 

UNITED STATES DEPARTMENT OF AGRICULTURE 
WASHINGTON, D. C. 




NEW EQUIPMENT FOR OBTAINING HOST MATERIAL 
FOR THE MASS PRODUCTION OF TRICHO- 
GRAMMA MINUTUM, AN EGG PARASITE 
OF VARIOUS INSECT PESTS 

By Heiebeet Spencek, entomologist, Luther Brown, associate entomologist, and 
Arthur M. Phhxips, ^eld assistant, Divisimi of Fruit Insect Investigations, 
Bureau of Entomology and Plant Quarantine 



CONTENTS 



Page 

Introduction 1 

Original equipment and technic 1 

Trays for rearing Sitotroga moths 1 

Method of procuring parasitization.--." 3 

Results obtained in 1931 and 1932 4 

Limiting factors and difficulties 5 

Improved equipment and technic 6 

Description of the cabinets 6 

Operation of the cabinets..- 7 



Page 

Improved equipment and technic — Con. 

Cost of operation in 1933 ii 

Production and costs in 1934 12 

Comparison of production costs 15 

Estimates of floor space, articles of equipment, 

and laborneeded 16 

Space requirements 16 

Equipment 16 

Labor 17 

Summary 17 



INTRODUCTION 

During the 4 years in which the Albany, Ga., parasite laboratory 
of the Bureau of Entomolog}^ and Plant Quarantine has been en- 
gaged in mass i)roduction of Tricho gramma minutum Kiley for 
experimental use, numerous changes in technic and apparatus have 
been made with the idea of increasing the output of beneficial insects 
and of reducing the cost of production. As soon as any modifications 
proved their value they were adopted, and the older equipment and 
methods were discarded. So many changes have been made during 
the 4 years that the present equipment and technic have little resem- 
blance to those used at the beginning. It is deemed advisable, there- 
fore, to describe at this time the improvements in the aj)paratus and 
methods. 

ORIGINAL EQUIPMENT AND TECHNIC 

Mass rearing of TricKogTamma minutum involves not only propa- 
gation of the j^arasites themselves but also the simultaneous produc- 
tion of vast numbers of host insects, in the eggs of which the para- 
sites develop. The Angoumois grain moth {Sitotroga cerealelloj 
Oliv.) is the host used for this purpose in most of the production 
laboratories. 

TRAYS FOR REARING SITOTROGA MOTHS 

The original equipment for multiplication of Sitotroga in the 
Albany laboratory consisted of four incubator rooms, 12 % 16 feet 



9405°— 35 1 



1 



2 CIRCULAR 3 7 6, U. S. DEPARTMENT OF AGRICULTURE 



with 7-foot ceilings, provided with racks holding double tiers of 
trays or " drawers " of corn, the trays being 36 inches wide, 24 inches 
from front to back, and nearly 4 inches deep, with bottom of 1/6-inch 
galvanized hardware cloth (fig. 1). Each tray was loaded with a 
bushel of Yellow Dent corn, making a layer 3 inches deep. Infesta- 




FiGUEB 1. — Collecting moths of Sitotroga cerealella in an incubator room from trays of 

infested corn. 



tion was started in this corn by the addition of eggs of jS. cerealella, 
and development was accelerated by keeping the incubator rooms at 
80° F. night and day and by spraying the rooms and infested corn 
twice weekly with water. 

Adult moths were collected from these rooms after three develop- 
mental cycles of the host had been completed, or about 90 days after 



MASS PRODUCTION OF TRICHOGRAMMA MINUTUM 3 



the eggs were introduced. The moths were gathered daily with the 
aid of a vacuum sweeper into a battery jar equipped with a separat- 
ing cover which prevented the moths from being drawn on into the 
machine (fig. 1). The battery jars containing the collected moths 
were fitted with 20-mesh brass screen-wire covers, held on with large 
rubber bands cut from inner tubes of automobile tires, and were kept 
in the oviposition racks for 3 days, the loose eggs being shaken 
through the screen-wire tops each morning (fig. 2). After cleaning 




Figure 2. — Removing eggs of Sitotrona moths from egg-deposition jars by shaking them 

through screen-wire tops. 



by fanning, the eggs were affixed with photograph paste (fig. 3) to 
circles of white cardboard. Each card was 314 inches in diameter 
and held approximately 50,000 eggs. 

METHOD OF PROCURING PARASITIZATION 

The iDarasite Trichogramiiia mhiutum was propagated in Petri 
dishes on a rack in an adjacent laboratory room (fig. 4). Ordinarih% 
one-fourth to one-half of a previously parasitized card of Sitotroga 
eggs was u^ed as a " starter and when the adult parasites had 
emerged a card of fresh eggs was inserted, and this was replaced on 



4 



CIKCULAE 3 7 6, U. S. DEPAETMEXT OF AGEICULTUEE 



the second day by another card. Four days after exposure to the 
parasites, the Sitotroga eggs in which Trichogravima was developing 
turned black, and 3 or 4 day^ later, at the 80° F. temperature, emer- 
gence of adults took place. In most of the field experiments, emerged 
adults of Trichogramma were liberated in orchards or fields from 




Figure 8. — Pasting Sitotroga eggs to cardboard circles. 



the Petri dishes used in production, but sometimes portions of para- 
sitized cards were hung in the trees with fine magnet wire to allow 
emergence to take place in the open air. It wa,s always necessary to 
• keep one-eighth to one-fourth of all the parasites for use as starters 
> in the laboratory. 




FiGUiiE -i. — Propagation of Trichogramma minittiim in Petri dishes by the use of cards of 

Sitotroga eggs. 



RESULTS OBTAINED IN 1931 AND 1932 

In 1931 only two incubator rooms were in operation, but these pro- 
duced a total of 25,444,000 Sitotroga eggs with this equipment and 
technic. The 1932 production was nearly 31,000,000. At the end of 
each rearing season a careful estimate was made of actual co,sts, in- 
cluding supplies, labor, heating, and depreciation on equipment, the 
last item being charged each year at one-tenth of the original cost. 



MASS PEODUCTIOlSr OF TEICHOGRAMMA MINUTUM 



5 



Xone of the expenses connected with other experiments, in the field 
or laborator3^ was included in these estimates, nor were the items 
of rent or cost of supervision. 

The following tabulation shows in detail the expenses incident to 
the production of host eg^s and the further handling of these in 
obtaining the desired parasites for the sea,son of 1931 : 



Permanent equipment : 

Racks, incubator rooms $81. 00 

Trays, incubator rooms 345. 00 

Refrigerator, electric 1.59. 39 

Furniture 1 9. 45 

Fans, incubator rooms 16. 00 

Cans, fumigating 20. 00 

Vacuum sweeper 32. 00 

Thermometers 29. 00 

Tops for jars 19. 00 

Miscellaneous 8. 65 



Total $719.49 



10 percent depreciation for year 71. 95 

Fuel (fuel oil) 63.75 

Electricity, gas, water ^ -. 80. 00 

Glassware and miscellaneous supplies: 

Battery jars 20.52 

Petri dishes 13. 00 

Graduated cylinders 2. 52 

Paste - 3. 50 

Cardboard . . 90 

Small items 8. 63 



Total ^ 49. 07 

Corn for rearing host insects, 200 bushels at $1.18 each 236. 00 

Labor : 

Moth collecting, 240 days, 4 hours each, at $0.15 per hour__ 144. 00 
Cleaning eggs, 240 days, 1 hour each, at $0.40 per hour___ 96. 00 

Pasting eggs, 25.5 hours at $0.40 per hour 10. 20 

Parasite propagation, 240 days, one-half hour each, at $1 

per hour ^ 120. 00 

Cleaning glass^vare, 240 days, 1 hour each, at $0.15 per 

hour ^ 36. 00 

Screening dirty corn 10. 00 



Total 416. 20 



' Total costs (1931)'^ 916.97 

Cost per million Sitotroga eggs (25,444,000 produced) 36.04 



There were but minor variations in some of the items in the work 
in 1932, but the cost per million of Sitotroga eggs was a little lower, 
as about a fourth more eggs were produced with only a slightly 
higher total cost. In 1931, 25,44:4,000 Sitotroga eggs were obtained 
at a cost of $916.97, or $36.04 per million. In 1932, 30,801,000 
Sitotroga eggs were obtained at a cost of $1,043.35, or $33.87 per 
million. 

LIMITING FACTORS AND DIFFICULTIES 

While these production figures compared quite favorably with 
those of other laboratories where mass rearing was being carried on, 
and with current commercial prices for the parasites, still larger 
yields and lower unit costs were desired. The limiting factor in the 



^ Estimated. - Average. ^ Rental and cost of supervision not included. 



6 CIRCULAE 3 7 6, U. S. DEPAETMENT OF AGEICULTUEE 

laboratory mass production of Tricho gramma was the number of 
host eggs that could be produced with the equipment described. If 
there had been available several times the number of host eggs actu- 
ally produced, all could have been used for breeding parasites with 
only a small additional outlay for apparatus and labor. This desired 
increase in production of host material could have been obtained by 
utilization of more grain, in additional incubator rooms, fitted out 
with equipment of the same kind. 

However, in the course of the production in 1931 and 1932, several 
rather serious defects appeared that led to a search for better host- 
rearing apparatus. In the first place the 3-inch layers of corn were 
wasteful, as the Sltotroga moths bred only in the kernels near the 
upper and lower surfaces. Shallower trays with only II/2 or 2 inches 
of corn would have produced as many moths as did the deeper 
trays, and in the same space there could have been a much larger 
number of them. When infestation became heavy in the incubator 
rooms, heating of the deep layers of corn occurred, and in hot 
weather this heat actually killed the Sltotroga stages and abruptly 
terminated production. Then, too, incubator rooms quickly be- 
came infested with such pests as gamasid mites, coleopterous weevils 
of several varieties, and a hymenopterous parasite {Dibvachys 
houeheanm Katz.). \Yhile the mites and weevils could be kept under 
control without difficulty, the parasite D. houcheamis proved to be 
a serious menace to mass production of Sitofroga^ as it could not 
be kept out of the incubator rooms even by the most careful screen- 
ing with 60-mesh screen wire, and very soon after gaining entrance 
to the rooms it reduced the hosts almost to extinction. 

IMPROVED EQUIPMENT AND TECHNIC 
DESCRIPTION OF THE CABINETS 

Upon the suggestion of S. A. Eohwer and C. P. Clausen, of the 
* Bureau of Entomology and Plant Quarantine, mass rearing of Sito- 
troga in wheat was tried in small cabinets of several designs.* In 
these preliminary tests it was clearly demonstrated that wheat was 
superior to corn for mass rearing of Sit of rag a^ but the shallow hori- 
zontal trays used in all the cabinets for holding the wheat were un- 
suited to the climate of southern Georgia, as excessive heating of the 
infested grain occurred in hot weather. A cabinet of original de- 
sign (fig. 5) remedying this and other unsuitable features was finally 
constructed in the laboratory. Essentially it consisted of a boxlike 
chamber, 291^ inches wide, 28 inches from front to back, and'24 inches 
high, supported on four legs 12 inches long. The framework was 
wood; the bottom, back, and top were of galvanized sheet iron; and 
the full-length door in front was of the same material. The sides 
were 60-mesh copper screen wire. The sheet metal and screening were 
tacked on the inside of the framework, so that the inside of the 
cabinet would have a minimum of angles in which the adult moths 
might lodge. Large tinned-metal funnels were soldered in inverted 
position over four GV^-inch holes in the metal top. Automatic collect- 



* Stanley E. Flanders, of Riverside, Calif.. Philip Garman, of New Haven, Conn., H. W. 
Allen, of Moorestown, N. J., and A. B. Baird, of Belleville, Ontario, kindly furnished 
unpublished details and photographs of their rearing cabinets. 



MASS PRODUCTION OF TEICHOGRAMMA MINUTUM 



7 



ing cans of cylindrical shape (fig. 6), with 60-mesh screen tops and 
screw-on bottoms with inverted funnels attached, fitted closely over 
the funnels on the cabinet top. 

Inside the cabinet narrow trays for the wheat (fig. 5) were hung 
vertically from a strip of wood on each side. Each tray was framed 
of one-half- by three-quarter-inch wood, and was 26 inches long, 
one-half inch thick, and 13l^ inches deep. One side of each frame 




FiGUEE 5. — The 1933 cabinet (Public Service Patent 1,974,549) with door open to show 
vertically hanging trays of infested wheat. 



was completely covered with 12-mesh enameled screen wire, and the 
other was covered similarly, except that a narrow slot was left open 
at the top, so that the grain might be added to the tray easily, and 
might be removed when no longer suitable for rearing the moths 
(fig. 'i^)- 

OPERATION OF THE CABINETS 

In the fall and winter of 1932-33 and the following spring, 16 
of these cabinets were made and put into operation, and after several 



8 



CIECULAE 3 7 6, U. S. DEPARTMEI^T OF AGEICULTUEE 



experiments a routine j^rocediire for starting infestation in these 
units was adopted. Seed wheat was fumigated in tight insecticide 
cans with carbon clisulphide, and was stored in these containers until 
needed. For each cabinet, about li'o bushels of this grain was soaked 




Figure 6. — Parts of the automatic collecting can : a, Funnel soldered to top of cabinet ; 
6, separate funnel with rim of screw lid attached ; c, can with wire-screen bottom to be 
inverted and screwed into the rim attached to the funnel 6. 



for 10 minutes in cold water, and was then placed in the 16 trays 
which were hung in a rack (fig. 8). Rack and trays of grain were 
immersed 3 minutes in a tank of water heated to 70° C. (158° F.). 









a ^ 


c 


*3 






m, * j 
M 'a 

9 % 















FiGUiiE 7. — Individual traj'S, one filled Avith wheat : a. Top bar ; 1), slot for filling and 

emptying tray ; c. c, braces. 



Still in the rack, the trays of wheat were drained and then for 3 days, 
or until just dry enough to avoid molding when placed in the cabi- 
nets, were dried in one of the incubator rooms which was free from 
flying moths. 

To start the infestation, 1,200,000 Sitotroga eggs on the cards 
were placed in eight of the vertical trays through the open slots, on 



MASS PRODUCTION" OF TEICHOGEAMMA MINUTUM . 9 

top of the masses of treated grain, and these trays were set in place 
in the cabinet. Two weeks later an equal number of eggs were placed 
in eight more trays, which were added similarly. By introducing 
the 2,400,000 eggs in 2 fractions, separated 14 days apart, marked 
peaks of emergence for the adult moths were avoided, and almost 
uniform daily production was attained. The cards of eggs were 




Figure 8. — Plunging loaded trays into the hot-water bath for disinfesting wheat and 

adding moisture. 



dipped momentarily in liquid carbon disulphide, for the elimination 
of mites and other pests, and were quickly dried. This treatment 
does not aifect the Sitotrogct eggs, which seem to be almost imper- 
vious. After 35 daj^s in the incubator rooms at 80° F., infestation 
had reached levels that were sufficiently high for the removal of the 
moths by use of the automatic collecting cans. The cabinets could 
be continued in full production for 2, and sometimes 3, months there- 

9405°— 35 2 



10 CIECULAE 3 76, U. S. DEPARTMENT OF AGEICULTUEE 

after. For a continuous production of 1,000,000 Sitotroga eggs per 
day, it was necessary to start 1 cabinet each week, the first unit 
being ready for restocking the week after the sixteenth was started ; 
the desired maximum being attained 12 weeks from the start, or 
when 8 cabinets were in full production. Thereafter this production 
was held uniform at this level as long as eggs were desired. By 
starting 2 cabinets each week, full production of 1,000,000 per day 
could probably be reached in 8 weeks. 

In 1933, with these 16 cabinets, a total of 125,110,000 Sitotroga 
eggs was obtained. Grain and eggs of S. cerealeUa were placed in 
the first of the cabinets in September 1932, and the infestation was 
built up during the winter and early spring of 1933 as rapidly as 
possible, all the eggs obtained from the first units having been uti- 
lized for infesting additional cabinets. Maximum production was 
reached during March 1933, in which month a total of 25,516,000 
eggs was produced. Production was held at about this level during 
April ancl May. On account of the improved ventilation for the 
grain in the cabinets, heating did not occur, and production was not 
discontinued during the summer, but was continued at a somewhat 
reduced level until the last of August. The production record, by 
months, for the 4 years is given in table 1. 



Table 1. — Laboratory production of Sitotroga eggs, by years and months, at 
Albany, Ga., 1931 to 1934 



Month 


1931 


1932 


1933 


1934 


November i _ _ . 


Number 


Number 


Number 

1, 012, 000 

2, 699, 000 

6, 151, 000 

7, 165, 000 
25, 516, 000 
24, 605, 000 
23, 722, 000 

13, 840, 000 

14, 800, 000 
5, 310, 000 

290, 000 


Number 


December i- _ . . . _ 








January. . . _ _ _ . - 


47, 000 
23, 000 
154, 000 
4, 092, 000 
9, 818, 000 
10, 480, 000 
830, 000 






February _ _ _ _ 






March- - _ 


4, 512, 000 
8, 880, 000 
12, 257, 000 
4, 874, 000 
278, 000 


23, 000 
1, 035, 000 
3, 055, 000 
3, 950, 000 

5, 000, 000 

6, 350, 000 
2,910,000 
5, 040, 000 

, 24,050,000 
24, 550, 000 


April _ 


May. . . . - _ . 


June - - - - 


July 


August -. - - .- . - _. _ 


September.- -.. . . . - - 


October . ._ _ _ . . _ _ . 












December. . _ . _ 








Total 








25, 444, 000 


30, 801, 000 


125, 110, 000 


75, 963, 000 



1 Of preceding year. 

2 Production discontinued for season. 



The operation of the new cabinets during 1933 was quite satisfac- 
tory, and only a few minor changes in their construction were neces- 
sary. Most of the difficulties experienced in 1931 and 1932 were 
solved. In the narrow trays none of the wheat grains escaped in- 
festation during the period in which the units were in production; 
thus there was no waste of grain. Ventilation in the cabinets was 
adequate. The heat of infestation in the narrow, vertical trays of 
grain assisted in the ventilation, and the more heating there was 
in the cabinet the faster this system of ventilation operated, since 
the hotter the air became between the trays the faster it rose and 
escaped. The hymenopterous parasite Dibrachys Ijoucheanus was kept 



MASS PEODUCTION OF TPJCHOGRAMMA MINUTUM 11 

out of the units hj the 60-mesh screening used on sides and on the 
collecting can3. The gamasicl mites and coleopterous weevils could 
still be found in the cabinets at the end of the production cycle, but 
these pests did not become abundant enough to influence the Sifo- 
troga infestation adversel}^ The initial routine treatments of the 
wheat and the thorough screening helped to bring about this 
improvement. 

From the standpoint of production the use of the cabinets was far 
superior to the incubator-room method previously employed. In this 
connection it is only necessary to point out that monthly production 
during each of the months of March, April, and May of 1933 nearly 
equaled or exceeded the total number of eggs produced during the 
entire year of 1931 (table 1). The use of the cabinets not onh" in- 
creased the gross yield of Sitotroga eggs but also decreased greatly 
the cost of production. The saving was especiallv noticeable in the 
cost of grain. In 1931 and 1932 56.000,000 eggs in all were ob- 
tained by the use of 400 bushels of corn purchased for $472 ; in 1933 
24 bushels of wheat costing $24.50 served for the production of more 
than 125,000,000 eggs in the cabinets. There was al^o a saving in 
labor. With the new automatic collecting cans on the tops of the 
cabinets, only a quarter to a half an hour of labor was necessary 
each day for gathering the moths where formerly 4 hours was devoted 
to the operation in the incubator rooms. 

COST OF OPERATION IN 1933 

An analj^sis of costs under the new technic employed with the 
cabinets revealed that the cost per millioru for the 125,110,000 eggs 
obtained in 1933 was $6.65. In the following tabulation there is a 
brief recapitulation of the items in the analysis of which these cost 
estimates were obtained: 



Permanent equipment : 

From previous years $327. 65 

Cabinets, 16 at $23.75 eacli 380. 00 

Ventilating fans, 3 at $8 each 24. 00 

Screen wire, 60-mesli 49. 50 

Hose for spraying 4. 50 



Total - $785.65 



'10 percent depreciation for 1933 78. 57 

Fuel (fuel oil) 97. 80 

Electricity, gas, water ' 120. 00 

Glassware and miscellaneous supplies : 

Battery jars 21.60 

Petri dishes 14. 50 

Cardboard 3. 00 

Paste 7. 85 

Fumigants 6. 75 

Miscellaneous . 11. 35 



Total 65. 05 

Wheat for rearing host insects : 

10 bushels at $1 10. 00 

10 bushels at $0.95 9. 50 

4 bushels at $1.25 5. 00 



Total - 24. 50 



^ Estimate. 



12 CIECULAE 3 7 6. U. S. DEPARTMENT OF AGRICULTURE 



Labor : 

Moth collecting, 330 days, 14 lioiir each, at $0.^0 per hour_ $33. 00 
Cleauiug eggs, 330 days, 1 hour each, at $0.40 per hoiir___ 132. GO 
Pasting eggs, 125 million, 1 hour each million, at $0.40 

per hour 50. 00 

Parasite propagation, 330 days, Y2 hour each, at $1 

per hour ° 165. 00 

Cleaning glassware, 330 days, 1 hour each, at $0.15 per 

hour ' 49. 50 



Total : $429.50 



Total costs ( 1933 ) ' 815. 42 

Cost per million Sitotroga eggs (125,110,000 produced) 6. 51 



For the purpose of protecting the rights of the public in this rear- 
ing device, and to make it available for use of anyone without pay- 
ment of fees or royalties, application for a public-service patent was 
made and, on September 25, 1934, Letters Patent No. 1974549 were 
granted. 

The securing of a public-service patent on this device was made 
possible through the courtesy of Arthur Gibson and A. B. Baird, of 
the entomological branch. Dominion of Canada Department of Agri- 
culture, and of Philip Garman, of the Connecticut Agricultural Ex- 
periment Station, in permitting the incorporation of certain original 
features of their own rearing units in modified form in the one here 
described. 

PEfODUCTION AND COSTS IN 1934 

Because of necessary economies, the mass rearing program for 
1934 was not started in the previous December as originally planned, 
but infestation of the first cabinets was delayed until February 10. 
There was an unexpectedly early demand for Trichogrcumna minu- 
tum for experimental releases in apple orchards in April and May, 
and this absorbed so many of the Sitotroga eggs produced by the 
» cabinets first infested that an insufficient number remained for proper 
infestation of cabinets put into operation later on. Then, too, full 
production was further retarded by the untimely appearance of the 
mite Pediculoides ventricosus Newport in five of the cabinets, Avhich 
were immediately fumigated with carbon disulphide to eliminate 
this pest. 

The fumigation was done by putting the cabinet into a specially 
constructed fumigation box, designed and made in the laboratory for 
the purpose (fig. 9). 

This box consisted of a shallow galvanized sheet-metal tray, rein- 
forced with wood, measuring 42 by 36 inches, by 1% inches deep, 
and a sheet-metal top, soldered gastight, measuring 45 inches high, 
35 inches from side to side, and 30 inches from front to back. Metal 
handles on this top and the light weight (52 pounds) made the outfit 
easily portable, and when in use the rearing cabinet was placed in the 
traylike bottom, the top was lowered over it until the open end 
lested inside of the bottom tray, and a layer of water in the latter 
elfectively sealed the box and allowed none of the fumigating gas 
to escape. Carbon disulphide was introduced through an opening 



^ Average. 

Rental and cost of supervision not included. 



MASS PEODUCTIOIs^ OF TRICHOGRAMMA MINUTUM 



13 



ill the top, provided with a screw-type lid, at the rate of 40 ml for 
the 33 cubic feet of space, and no mites or insect stages survived the 
fumigation period of 24 hours. The loss of the Sitotroga infestation 
in five cabinets which were fumigated prematurely because of con- 
lamination with Pediculoides was a serious setback to the rearing 
program, early in 1934. However, by thorough clean-up methods, 
and the use of the fumigation box, Pediculoides was successfully 
eliminated. 

In spite of a very late start and of the Pediculoides infestation, a 
total of 75,963,000 Sitotroga eggs was obtained during 1934 (table 
1). A peak yield approaching 1,000,000 host eggs per day was even- 
tually reached and the present program calls for continuance of this 
daily yield permanently by replacement of exhausted units regularly 



at weekly intervals with freshly stocked cabinets. During the year 
several small improvements were made in the design of the cabinet 
(fig. 10). New fronts hinged in the middle, with the upper part 
bolted tight to the unit and the lower hinged portion arranged so that 
debris might be removed from beneath the trays without loss of 
many moths, were attached to all of the units. Removal of dead 
moths, dust, and other waste products from the bottoms of the cabi- 
nets in this way helped to reduce the number of mites and weevils. 
It was found also that spraying the insides of the units and the trays 
of wheat twice daily with water materially increased production and 
induced larger proportions of the moths to enter the collecting cans. 

The reduction in total yield of Sitotroga eggs in 1934, as compared 
with 1933, and heavier expenses for humidifying equipment, espe- 
cially, made the cost per million eggs considerably higher than in 




Figure 9. — Fumigating box covering a cabinet. 



14 CIRCULAR 3 7 6, U. S. DEPARTMEITT OF AGRICULTURE 



1933. Careful estimates, as shown in the following tabulation, have 
given a cost figure for 1934 of $9.88 per million eggs, which is much 
lower, however, than the cost per million in 1931 or 1932, when the 
original equipment was in use. 




Figure 10. — The improved 1934 cabinet. 



Permanent equipment : 

From previous years $785. 65 

Humidifying equipment 120. 98 

Ventilating fans 16. 43 

Gas hot plate 7. 75 

Portable fumigating box 5. 23 

Tank for clipping grain 2. 00 



Total $938.04 



10 percent depreciation for 1934 93. 80 

Fuel (fuel oil) _i 119.20 

Electricity, gas, ^Yater ^ 100.00 

Glass\Yare and miscellaneous supplies : 

Battery jars 21.60 

Petri dishes 14. 50 

Cardboard 8. 00 

Paste '3. 35 

Fumigants 11. 92 

Miscellaneous 7. 00 



Total 6L 37 



s Estimate. 



MASS PKODUCTIOlSr OF TEICHOGEAMMA MINUTUM 



15 



Wheat for rearing liost insects : 

20 bushels at $1.35 $27. 00 

5 bushels at $1.60 — 8. 00 

Total $35. 00 

Labor : 

Moth collecting, 270 days, i/4 hour each, at $0.40 per hour_ 27. 00 

Cleaning eggs, 270 clays, 1 hour each, at $0.40 per hour — 108. 00 
Pasting eggs, 77 million, 1 hour each million, at $0.40 

per hour 30.80 

Parasite propagation, 270 days, i/^ hour each, at $1 per 

hour ' 135. 00 

Cleaning glassware, 270 days, 1 hour each, at $0.15 per 

hour ' 40. 50 

Total 341. 30 

Total costs (1934)" 750.67 

Cost per million Sitotroga eggs (75,963,000 produced) 9.88 

Since the refinements in design of cabinet, in humidifying equip- 
ment, and in technic were conceived late in the rearing season of 
1934, the benefits derived from their use do not show in the 1934 
mass-production results, but may be expected to show in later work. 
With the 16 cabinets in the Albany laboratory, it should be easily 
possible to obtain a continuous daily yield of 1,000,000 host eggs 
throughout the year, if desired; and by special manipulation of the 
cabinets and by infesting twice the number usually started at weekly 
intervals production can " undoubtedly be maintained at the peak 
for short periods, so that double this number of Sifotroga eggs 
may be obtained. 

COMPARISON OF PRODUCTION COSTS 

The totals for the different classes of costs in 1931, 1933, and 
1934 are presented in table 2. 

Table 2, — Cost of mass rearing of eggs of Sitotroga cerealella in 1931, 1933, ami 

1934, AlMmj, Ga. 



Item 


1931 


1933 


1934 


Depreciation in value of permanent equipment (10 percent) 
Fuel (fuel oil) 


$71. 95 
63. 75 
80. 00 
49. 07 
236. 00 
416. 20 


$78. 57 
97. 80 

120. 00 
65. 05 
24. 50 

429. 50 


$93. 80 
119. 20 
100. 00 
61.37 
35. 00 
341. 30 


Electricity, gas, water 1 


Glassware and miscellaneous supplies . _ . . 


Grain (corn or wheat) for rearing host insects . 
Labor. __ _ . . . . . .... 


Total 2 


916. 97 


815. 42 


750. 67 


Average cost per million Sitotroga eggs . - _ . 


36. 04 


6. 51 


9. 88 



1 Estimated. 

2 Rental and cost of supervision not Included. 



s Average. 

1" Rental and cost of supervision not Included. 



16 CIKCULAK 3 7 6, U. S. DEPARTMENT OF AGRICULTURE 

ESTIMATES OF FLOOR SPACE, ARTICLES OF EQUIPMENT, AND 

LABOR NEEDED 

The following estimates are for the production of 2,000,000 
Sitotroga eggs daily. 

SPACE REQUIREMENTS 

All rooms used should have provision for maintaining a constant 
temperature of 80° F., and if exact control is not feasible the tem- 
perature should never be allowed to exceed 94°. A controlled rela- 
tive humidity between 50 and 70 percent should be provided. 

STARTING EOOM 

Minimum floor space, 192 square feet. Used for treating grain 
with hot water, for starting the infestation in newly stocked cabinets, 
and for incubation in these until moths emerge (35 days). 

PRODUCTION EOOM 

Minimum space, 576 square feet. Cabinets producing moths are 
manipulated in this room. The total space may be in three separate 
rooms. 

OVIPOSITION AND PARASITE WORK 

Minimum floor space, 192 square feet. The egg-cleaning work 
should be partitioned off from the parasite-production space because 
of annoying dust. Two small rooms could be used. 

Total minimum floor space, 960 square feet. 

EQUIPMENT 

Starting room : 

1 liot-water treatment tank and accessories (fig. 8). 

10 tightly-covered cans for fumigation of grain, 

1 table, metal top, 2 by 3 feet. 

1 scoop for handling grain. 

1 tray, galvanized, 2 by 3 feet, 4 inches deep. 

1 metal fumigating box, 45 by 35 by 30 inches (fig. 9). 

1 fan, 10-inch, nonoscillating. 
Production rooms : 

24 cabinets for rearing moths (fig. 10). 

1 fan, 10-inch, nonoscillating, for each room. 

1 metal stool, 24 inches high, for each room. 

1 hose, 1/4 -inch, with spray nozzle, for each room. 
Oviposition room : 

1 set of seven shelves, 10 feet long, 1 foot deep, and 8 feet high. 

48 battery jars, 6% inches in diameter, 8 inches deep. 

48 screen-wire tops, 20-mesh, for jars. 

1 table, -metal top, 3 by 4 feet. 

300 Petri dishes. 

1 rack (fig. 4) for exposing Sitotroga eggs to parasites. 
1 electric refrigerator, small size. 
Miscellaneous supplies : 

100 pounds of carbon disulphide. 

3 respirators. 

1 sling psychrometer. 

4 maximum and minimum thermometers. 



MASS PRODUCTION" OF TEICHOGEAMMA MINUTUM 



17 



LABOR 



Skilled : 



Supervisiou 

Parasite propagation, 



Hours 
per day 

1 

— 1 



Unskilled : 



Collecting moths from cans on cabinets. 

Shaking eggs from oviposition jars 

Pasting eggs to egg cards 

Cleaning rooms and glassware 

Miscellaneous 



1 

1 
2 
1 
1 



SUMMARY 



In 1931 and 1932 the Albany, Ga., laboratory of the Bureau 
of Entomology, United States Department of Agriculture, engaged 
in mass rearing of the host Sitotroga cerealella Oliv. and the para- 
site Trichogramma m'lnutum Riley, and obtained total yields of 
approximately 25,444,000 and 31,000,000 host eggs in the respective 
years. For this work 200 bushels of corn were used each year in 
traj^s in two large incubator rooms. 

Careful cost estimates, derived from daily records kept through- 
out this period, indicated that the cost per million of the Sitotroga 
eggs was $36.04 in 1931 and $33.87 in 1932. 

Certain undesirable factors which adversely influenced produc- 
tion of Sitotroga eggs in large incubator rooms brought about experi- 
ments with several types of rearing cabinets and with other grains. 
These factors were : Waste of grain, inadequate ventilation which 
brought about heating, entrance of undesirable pests into the rooms, 
and relatively high costs. A new and improved cabinet for rearing 
the host insect was designed and patented. It utilized narrow 
vertical hanging trays of wheat and was fitted with automatic col- 
lecting devices. A device for treating grain with hot water for 
elimination of undesirable insects and mites and conditioning of 
the grain for starting rearing cabinets, is described. An infesta- 
tion of the mite Pediouloides ventHcosus Newport in rearing cabinets 
was eliminated by use of a metal fumigation box, featuring port- 
ability, gas-tight construction, and a traylike door sealed with a 
water layer during operation. 

In 1933 16 cabinets using 24 bushels of wheat costing only $24.50 
yielded more than 125.000,000 Sitotroga eggs. The cost per million 
was reduced to $6.51. In 1934, operating under a retarded program, 
75,963,000 eggs were obtained with a cost of $9.88 per million. 

In 1933 a peak production of more than 800,000 eggs per day 
was reached and held constant for a 3-month period. In 1934 a 
similar peak was reached, and production was being continued at 
a high level at the end of the year. 



ORGANIZATION OF THE UNITED STATES DEPARTMENT OF AGRICULTURE 
WHEN THIS PUBLICATION WAS LAST PRINTED 



Secretary of Agriculture Henry A, Wallace. 

Under Secretari/ . Rexfoed G. Tugwell. 

Assistant Secretary M. L. Wilson. 

Director of Extension Work C. W. Wakburton. 

Director of Personnel W. W. Stockbergek.. 

Director of Information M.S.Eisenhower. 

Director of Finance W. A. Jump. 

Solicitor Masiin G. White. 

Agricultural Adjustment Administration Chester C. Davis, Administrator. 

Bureau of Agricultural Economics A. G. Black. Chief. 

Bureau of Agricultural Engineering S. H. McCrory, Chief. 

Bureau of Animal Industry John R. Mohler, Chief. 

Bureau of Biological Survey : Ira N. Gabrielson, Chief. 

Bureau- of Chemistry and Soils H. G. Knight, Chief. 

Bureau^ of Dairy Industry O, E, Reed, Chief. 

Bureau, of Entomology and Plant Quarantine-- Lee A. Strong, Chief. 

Office of Experiment Stations James T. Jardine, Chief. 

Food and Drug Administration Walter G. Campbell, Chief. 

Forest Service Ferdinand A. Silcox. Chief. 

Grain Futures Administration J. W. T. Duvel, Chief. 

Bureau of Home Economics Louise Stanley, Chief. 

lAhrary Claribel R. Barnett, Librarian. 

Bureau of Plant Industry Frederick D. Richey, Chief. 

Bureau of PuUic Roads Thomas H. MacDonald, Chief. 

Soil Conse7'vation Service H. H. Bennett, Chief. 

Weather Bureau Willis R. Gregg, Chief. 



This circular is a contribution from 

Bureau of Entomology and Plant Quarantine L. A. Strong, Chief. 

Divison of Fruit Insect Investigations..^ D. L. Van Dine, Principal Ento- 
mologist, in charge. 

18' 



U. S. GOVERNMENT PRINTING OFFICE: 1935 



For sale by the Superintendent of Documents, Washington, D. C. 



Price 5 cents